GB1190560A - Telephone Systems. - Google Patents

Abstract

1,190,560. Automatic exchange systems. STROMBERG-CARLSON CORP. 10 July, 1967 [21 July, 1966], No. 31571/67. Heading H4K. In a switching network each link circuit has its own originating and terminating transistor cross-point matrices, subscribers' lines having no line circuits and being multipled over corresponding appearances in the matrices of each link circuit. In a link circuit the terminals of a feed transformer 10, shown partly in Fig. 1 and partly in Fig. 2, are each multipled to the rows of 10 x 10 matrices by way of coupling transistors such as 26-29. Each of the two wires of a subscriber's line is connected to the collector of corresponding transistor cross-points in the originating matrices of Fig. 1 and is similarly connected to the collectors of corresponding cross-points in the terminating matrices of Fig. 2. When allotted for use the originating matrices of a link are scanned by applying suitable potentials on the row and column leads so as to sequentially prime the transistors in each leg of each subscriber's line. If a line so scanned is looped in the calling condition, the matrix transistors in each leg conduct and relay ARS operates to seize the link and connect a register. Line scanning is now transferred to the next link allotted for use. Busy testing and termination to wanted lines is effected in an orthodox manner. Diodes in the collector circuits allow a large cut-off bias to guard the cross-points against transients. Diodes in the emitter circuits provide protection against reverse breakdown voltages. The transistors in each leg of a line are preferably of opposite type, as shown.